RESEARCH

The evolution of competition among herbivores

The spider mites Tetranychus urticae and T. evansi co-occur on tomato. This plant can accumulate different amounts of cadmium in its aerial parts, creating a heterogeneous environment for the mites. We are investigating the consequences of this heterogeneity for the outcome of competition and how it interacts with other ecological factors such as plant defences. This information will allow testing how evolution in different environments affects intra- and interspecific competition in spider mites.

The ecological consequences ​of plant-mite interactions

​Whereas T. urticae induces plant defences, as most herbivores, T. evansi suppresses these defences on tomato. We are studying whether this ability is modified by the environment or by the evolutionary history of the mites.

Intraspecific variation, genetic correlations and species coexistence

Intraspecific trait variation and their correlation may affect the ecology and evolution of species coexistence. We are addressing (a) the potential correlation between variation in growth rates and carrying capacity, among reproductive traits and between behavioural and life-history traits (in spiders); (b) how individual variation in reproductive interference, niche width and in defence manipulation affects species coexistence.

​Mite-endosymbiont interactions

Wolbachia is arguably the most common bacterial reproductive manipulator in arthropods. We are investigating its effects on spider mite reproduction and mating strategies, as well as the factors (e.g. host plants, pesticide resistance or pathogens of spider mites) that affect its interactions with the host. We are also addressing how such factors affect the distribution of Wolbachia and that of other endosymbiotic bacteria in natural spider mite populations.

Reproductive isolation

Spider mite species/populations exhibit different degrees of reproductive isolation. We are testing how different factors, such as endosymbionts, ecological specialization (i.e. host plant use), reproductive interference and competition affect isolation patterns. Conversely, we are addressing how reproductive isolation affects the outcome of competition and the likelihood of coexistence.

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Mating strategies

In spider mites, the first male sires virtually all of the offspring. However, spider mites still mate multiply. We are investigating this paradox from several angles, from the mechanistic basis of mate recognition to the eco-evolutionary implications of first male precedence.